Personal trainers, retired athletes and professionals seeking a departure from the corporate grind are among the nontraditional investors opening new locations. This gives them a piece of a unique industry, one that is evolving as big-box gyms make way for smaller studios.

Fitness franchisees in the United States are expected to make $4.3 billion in revenue across nearly 10,000 locations this year, and forecasts show continued growth over the next four years, according to the market research firm IBISWorld.

But while business conditions favor fitness companies that want to expand through franchising, it’s the nature of the business itself that has also helped turn would-be investors into owners.

“Fitness franchising gives someone who gets a kick out of wellness—which should be all of us—a means of generating an income and creating a lifestyle that is more aligned with his or her own values,” said Luke Armstrong, global head of sales for F45 Training, a franchise that started in Sydney and now has several hundred locations in the United States.

Many F45 franchisees belong to one of four distinct groups, revealing seemingly divergent career paths that somehow meet in the same place—feeling gratified as a business owner for reasons that go beyond profitability.

Excerpts have been edited for clarity.

Why She Did It:

A marketer turned personal trainer, Jampolis put her life savings into opening one of the first F45 locations in the United States three years ago. “As a franchise owner, I get a little flexibility to be at my kids’ events, but I also get the mental stimulation and critical thinking that I missed in the corporate world.”

Secret to Her Success:

…I’m not motivated by money, I’m motivated by making an impact on people’s health and fitness. A lot of people worry about the launch and not the client experience. We pay attention to the little things, and we pay our coaches well because they’re not just cheerleaders.”

What Fitness Means to Her:

“Because I have kids, my workout is my sanity hour, my time to go and do something for myself. I grew up as an athlete, so exercise has always been my lifeline to achieve balance and feel a connection with people outside of work or my kids.”

Why He Did It:

A former professional hockey player, Meyer helped a friend open an F45 studio while living in Dubai. “It started as a selfish endeavor. When I moved back to Minneapolis, there was no F45. I wanted these workouts, so I decided to open a studio along with some female partners who were well-connected in the fitness community.”

Secret to His Success:

What Fitness Means to Him:

“Longevity. My body took serious abuse from hockey, and after I lost fitness I started to really feel those injuries. Now I feel much better.”

Why He Did It:

Arnberg spent his early career working in his family business, where he learned that all the details matter. “I like to be involved in everything, so I came to realize that I needed to own a business where no one was going to say, ‘Get out of my space.’” Arnberg worked in sales and marketing for pro sports teams, an art gallery and a national florist before buying an F45 franchise. “I thought, ‘This is exactly what I want to do, and everything’s all set up for me.”

Secret to His Success:

“I am there as many hours as I can be, teaching classes, taking classes with members. In the boutique fitness world, people want to feel a connection to the owner. You have to be all in.”

What Fitness Means to Him:

Why He Did It:

Formerly an oil company engineer, Murphy sought a franchise where he could put his business education to work. He checked out food and juice franchises before investing in F45. “I loved the product. It’s not goat yoga or something gimmicky. It’s a relatively low upfront investment, and I loved the sense of community the gyms create.”

Secret to His Success:

Murphy will soon open his third Houston-area F45 location with partner Milton Lewis, a trainer and gym manager.

…Many register but don’t show up; they’re afraid, or they haven’t worked out in a while. It’s good to reach out to these people and send the message that F45 is for everybody.”

What Fitness Means to Him:

“It’s more about long-term health so when I’m older I can play catch with my grandson. It’s not about being a bulky musclehead.”